Wells are generally drilled into a land surface or ocean bed to recover natural deposits of oil and gas, as well as other natural resources that are trapped in geological formations in the Earth's crust. Testing and evaluation of completed and partially finished wellbores has become commonplace, such as to increase well production and return on investment. Information about the subsurface formations, such as measurements of the formation pressure, formation permeability, and recovery of formation fluid samples, may be useful for predicting the economic value, the production capacity, and production lifetime of a subsurface formation. Downhole tools, such as formation testers, may perform evaluations in real-time during sampling of the formation fluid.
These testing and evaluation operations have become increasingly expensive as wellbores are drilled deeper and through more difficult materials. In working with deeper and more complex wellbores, it becomes more likely that tool strings, tools, and/or other downhole apparatus may include numerous testing, navigation, and/or other tools, resulting in increasingly large tool strings that consume increasingly larger quantities of electrical power to drive or otherwise energize various internal components of such tool strings. As an increasingly larger amount of power is consumed, increasingly larger amount of heat may be generated by the various internal components of the downhole tool, substantially raising their temperature. Moreover, the heat generated by the internal components of the downhole tool may not be dissipated at a sufficient rate, resulting in internal temperatures exceeding functional temperature limits.
Downhole tools may also be subjected to a variety of loads, including but not limited to pressure differential, tension, compression, hydraulic force, torsion, bending, shock, and vibrations. Shock loads (e.g., sudden changes in acceleration) are especially damaging to internal electronic components, and may occur while the downhole tool is being operated downhole, transported, or otherwise handled. For example, a shock load may occur when the downhole tool collides with another object at a high velocity. Such shock loads may be transmitted to an internal support structure (e.g., a chassis) of the downhole tool, and the internal electronic components coupled thereto, through various mechanical interfaces between the internal support structure and an exterior housing of the downhole tool. Moreover, the shock loads imparted to the downhole tool housing may be amplified when transmitted to the internal support structure if there is a gap between the downhole tool housing and the internal support structure. Shock isolators or dampers, which are typically made of elastomers, plastics, and/or other non-metallic materials, may thus be incorporated in the downhole tool to mitigate such amplification and/or shock transmissibility. However, due to low thermal conductivities of non-metallic materials, such shock isolators provide a poor thermal path for transferring heat generated by the internal electronic components to the downhole tool housing for dissipation into the operating environment.